The goal is to provide Debian and Ubuntu nightly packages ready to be installed with minimal impact on the distribution.
Packages are available for amd64, i386 (except for recent Ubuntu), s390x and arm64 (aka aarch64). This for both the stable, qualification and development branches (currently 14, 15 and 16).

Packages are built using stage2 and extremely similar to the one shipping in Debian & Ubuntu.

The packages provide LLVM + Clang + compiler-rt + polly + LLDB + LLD + libFuzzer + libc++ + libc++abi + openmp + libclc + libunwind + MLIR

Jul 31th 2022 - Snapshot becomes 16, branch 15 created
Jul 24th 2022 - Ubuntu Hirsute (21.04) and Impish (21.10) disabled (EOL)
Feb 18th 2022 - Ubuntu Jammy (22.04) enabled
Feb 04th 2022 - Snapshot becomes 15, branch 14 created
Jan 16th 2022 - llvm.sh can now install all packages at once with the 'all' option
Jan 15th 2022 - Sources and dsc files are signed on sigstore
Dec 30th 2021 - MLIR packages added from 13
Dec 23th 2021 - Ubuntu Groovy (20.10) disabled (EOL)
Dec 22nd 2021 - arm64 supported
Nov 02nd 2021 - Infra moved to the cloud
Oct 05th 2021 - Ubuntu Impish (21.10) enabled
Aug 01st 2021 - Snapshot becomes 14, branch 13 created
Aug 01st 2021 - libunwind packages are generated (libunwind-XX & libunwind-XX-dev)
Jul 25th 2021 - Packages are tested against the LLVM integration test suite
May 01st 2021 - libclc packages generated from 12. Thanks to Timo Aaltonen
Apr 25th 2021 - S390X support added
Mar 28th 2021 - Ubuntu Xenial (16.04) disabled (EOL)
Feb 01st 2021 - Snapshot becomes 13, branch 12 created
Feb 01st 2021 - Debian Bullseye (11) added

For convenience there is an automatic installation script available that installs LLVM for you.
To install the latest stable version:

bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)"

To install a specific version of LLVM:

wget https://apt.llvm.org/llvm.sh
chmod +x llvm.sh
sudo ./llvm.sh <version number>

To install all apt.llvm.org packages at once:

wget https://apt.llvm.org/llvm.sh
chmod +x llvm.sh
sudo ./llvm.sh <version number> all
# or
sudo ./llvm.sh all

Stretch (Debian 9 - old-old-stable) - Last update : Sat, 24 Sep 2022 12:54:59 UTC / Revision: 20220924115356+75279aeecd1d

deb http://apt.llvm.org/stretch/ llvm-toolchain-stretch main
deb-src http://apt.llvm.org/stretch/ llvm-toolchain-stretch main
# NOTE: as Stretch doesn't provide libstdc++ 7.1 or later, clang-16 is built against libc++
# 14 
deb http://apt.llvm.org/stretch/ llvm-toolchain-stretch-14 main
deb-src http://apt.llvm.org/stretch/ llvm-toolchain-stretch-14 main
# NOTE: as Stretch doesn't have gcc 7.1, from -15, stage1 is built using clang-14
# 15 
deb http://apt.llvm.org/stretch/ llvm-toolchain-stretch-15 main
deb-src http://apt.llvm.org/stretch/ llvm-toolchain-stretch-15 main

Buster (Debian 10 - old-stable) - Last update : Sat, 24 Sep 2022 14:15:56 UTC / Revision: 20220924115213+75279aeecd1d

deb http://apt.llvm.org/buster/ llvm-toolchain-buster main
deb-src http://apt.llvm.org/buster/ llvm-toolchain-buster main
# 14 
deb http://apt.llvm.org/buster/ llvm-toolchain-buster-14 main
deb-src http://apt.llvm.org/buster/ llvm-toolchain-buster-14 main
# 15 
deb http://apt.llvm.org/buster/ llvm-toolchain-buster-15 main
deb-src http://apt.llvm.org/buster/ llvm-toolchain-buster-15 main

Bullseye (Debian 11 - stable) - Last update : Thu, 22 Sep 2022 09:20:27 UTC / Revision: 20220922071802+e500f8f8a826

deb http://apt.llvm.org/bullseye/ llvm-toolchain-bullseye main
deb-src http://apt.llvm.org/bullseye/ llvm-toolchain-bullseye main
# 14 
deb http://apt.llvm.org/bullseye/ llvm-toolchain-bullseye-14 main
deb-src http://apt.llvm.org/bullseye/ llvm-toolchain-bullseye-14 main
# 15 
deb http://apt.llvm.org/bullseye/ llvm-toolchain-bullseye-15 main
deb-src http://apt.llvm.org/bullseye/ llvm-toolchain-bullseye-15 main

sid (unstable) - Last update : Thu, 22 Sep 2022 12:22:57 UTC / Revision: 20220909072630+a3a8bd00c8f1

deb http://apt.llvm.org/unstable/ llvm-toolchain main
deb-src http://apt.llvm.org/unstable/ llvm-toolchain main
# 14 
deb http://apt.llvm.org/unstable/ llvm-toolchain-14 main
deb-src http://apt.llvm.org/unstable/ llvm-toolchain-14 main
# 15 
deb http://apt.llvm.org/unstable/ llvm-toolchain-15 main
deb-src http://apt.llvm.org/unstable/ llvm-toolchain-15 main

Precise, Quantal, Raring, Saucy, Utopic, Artful, Cosmic, Eoan and Trusty are no longer supported by Ubuntu. Repo remains available but not updated.

As i386 isn't supported by Ubuntu anymore, apt.llvm.org isn't either.

Bionic LTS (18.04) - Last update : Sat, 24 Sep 2022 11:41:08 UTC / Revision: 20220924091515+de3efd1b4c8e

deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic main
deb-src http://apt.llvm.org/bionic/ llvm-toolchain-bionic main
# Needs 'sudo add-apt-repository ppa:ubuntu-toolchain-r/test' for libstdc++ with C++20 support
# 14
deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-14 main
deb-src http://apt.llvm.org/bionic/ llvm-toolchain-bionic-14 main
# 15
deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-15 main
deb-src http://apt.llvm.org/bionic/ llvm-toolchain-bionic-15 main

Focal (20.04) LTS - Last update : Fri, 23 Sep 2022 19:55:27 UTC / Revision: 20220923052629+2c692d891ed6

deb http://apt.llvm.org/focal/ llvm-toolchain-focal main
deb-src http://apt.llvm.org/focal/ llvm-toolchain-focal main
# 14
deb http://apt.llvm.org/focal/ llvm-toolchain-focal-14 main
deb-src http://apt.llvm.org/focal/ llvm-toolchain-focal-14 main
# 15
deb http://apt.llvm.org/focal/ llvm-toolchain-focal-15 main
deb-src http://apt.llvm.org/focal/ llvm-toolchain-focal-15 main

Jammy (22.04) LTS - Last update : Sat, 24 Sep 2022 06:23:09 UTC / Revision: 20220924042306+afb0b21f24ad

deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy main
deb-src http://apt.llvm.org/jammy/ llvm-toolchain-jammy main
# 14
deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-14 main
deb-src http://apt.llvm.org/jammy/ llvm-toolchain-jammy-14 main
# 15
deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-15 main
deb-src http://apt.llvm.org/jammy/ llvm-toolchain-jammy-15 main

To make sure always the most recent versions of the packages are installed, we are providing some default packages.
To install all of them (currently version 16):

apt-get install clang-format clang-tidy clang-tools clang clangd libc++-dev libc++1 libc++abi-dev libc++abi1 libclang-dev libclang1 liblldb-dev libllvm-ocaml-dev libomp-dev libomp5 lld lldb llvm-dev llvm-runtime llvm python3-clang

To retrieve the archive signature:

wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add -
# Fingerprint: 6084 F3CF 814B 57C1 CF12 EFD5 15CF 4D18 AF4F 7421

To install just clang, lld and lldb (14 release):

apt-get install clang-14 lldb-14 lld-14

To install all key packages:

# LLVM
apt-get install libllvm-14-ocaml-dev libllvm14 llvm-14 llvm-14-dev llvm-14-doc llvm-14-examples llvm-14-runtime
# Clang and co
apt-get install clang-14 clang-tools-14 clang-14-doc libclang-common-14-dev libclang-14-dev libclang1-14 clang-format-14 python3-clang-14 clangd-14 clang-tidy-14
# libfuzzer
apt-get install libfuzzer-14-dev
# lldb
apt-get install lldb-14
# lld (linker)
apt-get install lld-14
# libc++
apt-get install libc++-14-dev libc++abi-14-dev
# OpenMP
apt-get install libomp-14-dev
# libclc
apt-get install libclc-14-dev
# libunwind
apt-get install libunwind-14-dev
# mlir
apt-get install libmlir-14-dev mlir-14-tools

To retrieve the archive signature:

wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add -
# Fingerprint: 6084 F3CF 814B 57C1 CF12 EFD5 15CF 4D18 AF4F 7421

To install just clang, lld and lldb (15 release):

apt-get install clang-15 lldb-15 lld-15

To install all key packages:

# LLVM
apt-get install libllvm-15-ocaml-dev libllvm15 llvm-15 llvm-15-dev llvm-15-doc llvm-15-examples llvm-15-runtime
# Clang and co
apt-get install clang-15 clang-tools-15 clang-15-doc libclang-common-15-dev libclang-15-dev libclang1-15 clang-format-15 python3-clang-15 clangd-15 clang-tidy-15
# libfuzzer
apt-get install libfuzzer-15-dev
# lldb
apt-get install lldb-15
# lld (linker)
apt-get install lld-15
# libc++
apt-get install libc++-15-dev libc++abi-15-dev
# OpenMP
apt-get install libomp-15-dev
# libclc
apt-get install libclc-15-dev
# libunwind
apt-get install libunwind-15-dev
# mlir
apt-get install libmlir-15-dev mlir-15-tools

To retrieve the archive signature:

wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add -
# Fingerprint: 6084 F3CF 814B 57C1 CF12 EFD5 15CF 4D18 AF4F 7421

We also provide meta packages to move from a major version to the other.
For example, to automatically upgrade to the current major:

apt-get install clang lld # clang-16 lld-16 can be added to automatically install the most recent version of the package.

To install just clang, lld and lldb (16 release):

apt-get install clang-16 lldb-16 lld-16

To install all key packages:

# LLVM
apt-get install libllvm-16-ocaml-dev libllvm16 llvm-16 llvm-16-dev llvm-16-doc llvm-16-examples llvm-16-runtime
# Clang and co
apt-get install clang-16 clang-tools-16 clang-16-doc libclang-common-16-dev libclang-16-dev libclang1-16 clang-format-16 python3-clang-16 clangd-16 clang-tidy-16
# libfuzzer
apt-get install libfuzzer-16-dev
# lldb
apt-get install lldb-16
# lld (linker)
apt-get install lld-16
# libc++
apt-get install libc++-16-dev libc++abi-16-dev
# OpenMP
apt-get install libomp-16-dev
# libclc
apt-get install libclc-16-dev
# libunwind
apt-get install libunwind-16-dev
# mlir
apt-get install libmlir-16-dev mlir-16-tools

Source, Debian tarballs and dsc files can be verified using sigstore/rekor.
This can be done with "rekor verify":

file="llvm-toolchain-10_10.0.1~%2b%2b20210327072807%2bef32c611aa21-1~exp1~20210327183412.212.dsc"
url="https://apt.llvm.org/unstable/pool/main/l/llvm-toolchain-10/$file"
sig_file="$url.asc"
wget --quiet https://apt.llvm.org/sigstore.public.key
./rekor verify --rekor_server https://rekor.sigstore.dev --signature $sig_file --public-key sigstore.public.key --artifact $url
echo $?

Or with "rekor search":

file="llvm-toolchain-10_10.0.1~++20210327072807+ef32c611aa21.orig.tar.xz"
url="https://apt.llvm.org/unstable/pool/main/l/llvm-toolchain-10/$file"
wget --quiet $url
sha=$(sha256sum $file|awk '{print $1}')
./rekor search --sha sha256:$sha --rekor_server https://rekor.sigstore.dev

Packages are rebuilt against the trunk of the various LLVM projects.
They are rebuild through a Jenkins instance:
https://llvm-jenkins.debian.net

Bugs

Bugs should be reported on the LLVM bug tracker (label: packaging).

Workflow

Twice a day, each jenkins job will checkout the debian/ directory necessary to build the packages. The repository is available on the Debian hosting infrastructure: https://salsa.debian.org/pkg-llvm-team/llvm-toolchain/.
Sources of this page, llvm.sh and others scripts are available on github:
https://github.com/opencollab/llvm-jenkins.debian.net/
In the llvm-toolchain-*-source, the following tasks will be performed:

• upstream sources will be checkout
• The tarball will be created. It is named: llvm-toolchain-X_X.Y.Z~++DATE+UPSTREAM_COMMIT_HASH.orig.tar.xz
• Debian .dsc package description is created
• Start the jenkins job llvm-toolchain-X-binary

Then, the job llvm-toolchain-X-binary will:

• Create a chroot using cowbuilder or update it is already existing
• Build all the packages
• Launch lintian, the Debian static analyzer
• Publish the result on the LLVM repository

Note that a few patches are applied over the LLVM tarballs (and should be merged upstream at some point).

With the Jenkins instance, several reports are produced:

• Scan build report
• Coverity reports

Building LLVM packages from source is documented in a dedicated page.